Electric circuit breaker



ELECTRIC CIRCUIT BREAKER Filed April 23, 1940 Figi.

Inventors: Ralph d. Baskejv I I e, Benjamin E. Spiro,

, L L'Dy imei? Attorney Patented Apr. 8, 1941 ELECTRIC CIRCUIT BREAKERRalph J. Baskerville, Yeadon, and Benjamin E. Spiro, Philadelphia, Pa.,assignors to General Electric Company, a corporation of New YorkApplication April 23, 1940, Serial No. 331,148

` 3 claims.

Our invention relates to electric circuit breakers and more particularlyto a pressure contact hinge for circuit breakers employing pivotallymounted switch blades.

Pivotally mounted switch blades have been used for a great many yearsand the prior art is yreplete with disclosures of arrangements forimproving the hinge contacts' of such switches.

The main concern in pivotally mounted switch' blades is that ofproviding good electrical contact at the hinge which becomesparticularly important in circuit breakers where relatively largecurrents vare carried since such hinge contacts are likely to be asource of difficulty. In order to-improve the current-carrying capacityof such switches employing hinged switch blades, the contact areas ofthe hinged members were decreased ind the Contact pressure wasincreased.An arrangement of this type is disclosed and claimed in copendingapplication of Weder et al., Serial No. 314,826, filed January 20, 1940,and assigned to the same assignee as the present application. `In orderto obtain the desired contact pressure at the hinge, switches heretoforehave used the conventional convex-like phosphor-bronze spring washerswhich have given very satisfactory operation in connection withdisconnecting switches and the like. Diiculties, however, have beenenmounted switch blades which will overcome the.

disadvantages set forth above. A

It is another object of our invention to provide a new and improved highpressure contact hinge for circuit breakers employing a pivotallymounted switch blade which is capable of carrying large currentseiiciently, which is simple and compact, and which will givelong andsatisfactory service in all respects.

Further objects and advantages of our inven-v tion will become apparentas the following description proceeds and the features of novelty whichcharacterize our invention will' be pointed out with particularity in'the claims annexed to and forming a part of this specification.

For a better understanding of our invention,

reference maybe had to the following description countered when usingsuch Washers at the contact hinge of high-speed circuit breakersemploying a pivotally mounted switch blade. These diiilculties are dueto the fact that such spring washers have a very high pressure gradient,are

easily overstressed and subject to permanent set particularly if theyundergo a slight side play overhauling purposes, subsequent adjustmentby bodily lowering of the circuit breaker;

inexpert persons may vary considerably from the hinge for circuitbreakers employing pivotally taken in connection with 'the accompanyingdrawing in which Fig. 1 illustrates a circuit breaker embodying ourinvention and Fig. 2 is a sectional viewtaken on line 2-2 of Fig. 1 toillus- Although ourl invention is of general applica- 'tion in so far aspressure contact hinges for pivot. ally mounted switch blades areconcerned, we

have shown our invention as applied to an electric air circuit breakerof the type disclosed and broadly claimed in copen'ding application,Serial No. 298,946, filed October 11 1939, on behalf of Leonard J.Linde, and assigned to the assignee of the present application.

Referring now to Fig. 1, we have shown a circuit breaker I Il of thewell-known drop-down type for usein a grounded metalf enclosure orcubicle, not shown, wherein disconnection from the external electriccircuit is eiected merely by Circuit breaker Ill includes a movablecontact structure which comprises a fixed contact I I and a movablecontact I2 which is supported on almultiple knife blade or lever I3pivotally mounted at pressure contact hinge I4 to the' lower end ofconductor stud I5. Fixed contact I I'is mounted to the lower end ofconductor stud I6. Circuit Abreaker I0 also includes a suitablearc-extinguishing structure I1 and an actuating mechanism i8 which maybe connected to pivotally mounted multipleblade or lever I3 throughoperating` rod I9.

Referring now to Fig. 2 illustrating the pressure contact hinge I Ibetween stud I5 and movable multiple blade or lever I3, we have shown apair of hinge pintles 20 comprising cup-shaped members each providedwith a flanged lip 2I'. These cup-shaped members are arranged to beinserted in the cooperating openings I3a and I5a formedI of switchblades I3. -Coil springs 22 are inserted in the cup-shaped pintlemembers 2li and a suitable fastening means, such as bolt 23 includingnut 24, is `provided for stressing the springs 22 to give the desiredcontact pressure. It will be' observed that a very compact pressurecontact hinge is obtained by this arrangement since the spring membersare contained within the pintle. The pressure contact hinge Il,therefore, requires no morespace than the prior-art arrangement referredto above employing spring washers, and,` .at the same time, theadvantage of a low gradient-pressure means is obtained.

In order to improve the current-carrying capacity of pressure contact'hinge I4, we provide on one of the juxtapositioned surfac of pivotedswitch blades I3 or stud l5, contact surfaces 25 of restricted areaformed of a material, such as silver, the oxide of which is physicallyand chemically unstable so as not to interfere with electrical currentconduction. These contact surfaces 25 are preferably formed of anannular ring of silver which is placed in a shallow groove 26 and bondedto one of the juxtapositioned surfaces which contains the groove 26 byany suitable manner. An electric switch embodying such a raisedrestricted contact surface formed of ja' metal like silver is disclosedand broadly claimed in the above-mentioned copending application ofWeder et al.

It will, therefore, be noted that We have provided a rugged and compactpressure contact hinge for a pivotally mounted switch blade for use inconnection with high-speed circuit breakers carrying'relatively largecurrents wherein the contact pressure by virtue of the low-gradientspring means employed will remain substantially constant irrespective ofwear on the contact surfaces..

. While we have described a particular embodiment of our invention, itwill be obvious to those skilled in the art that various changes andmodifications may be made without departing from 4our invention and we,therefore; aim inthe apin switch blades I3 and stud l5, respectively, so

pended claims to cover all such changes andt-hat the flanged lips 2lengage with the surfaces v modifications as fall within the true spiritan scope of our invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. In a pivoted electrical connection, a. currentconducting member, acurrent-carrying bar, means for pivotally mounting said bar to saidcurrent-conducting member to provide an electrical pressure contacttherebetween comprising a cup-shaped pintle having a ange for engagingone of said members, a low pressure-gradient spring mounted within saidpintlefand means cooperating with said spring for producing asubstantially constant pressure between said current-conducting memberand said bar.

2. In a high-speed electric circuit breaker, a hinge member, a blademember pivoted on said hinge by means of a cup-shaped pintle including aflange for engaging oneof said members, a low pressure-'gradient springmounted within said pintle, and fastening means cooperating with saidspring for producing a substantially constant pressure between thejuxtapositioned surfaces of said members, one of said juxtapositionedsurfaces being provided with a raised restricted contact surface formedof a metal whose oxide does. not substantially interfere with electricalcurrent conduction.

3. In an electric circuit breaker, a currentconducting member, amultiple-blade switch member, means for pivotally mounting saidmultiple-blade switch member to said current-conducting member toprovide a pressure contact therebetween comprising a pair of cup-shapedpintles, each provided with a flange for engaging said multiple-bladeswitch member, -a pair vof low pressure-gradient springs mounted withinsaid pintles, and meansl cooperating with said springs and pintles forproducing a substantially constant pressure between saidcurrent-conducting member and said multiple-blade switch member.

` RALPH J. BASKERVILLE.-

BENJAMIN E. SPIRO.

